VL6180X proximity, gesture and ambient light sensing (ALS) module

Transcription

1 User manual VL6180X proximity, gesture and ambient light sensing (ALS) module Introduction The VL6180X is a proximity, gesture and ambient light sensor based on ST s patented FlightSense technology. The VL6180X interfaces to your micro-controller via the industry standard I²C bus. This user manual contains: VL6180X hardware information (Application schematic, Mechanical data, soldering process). List of available VL6180X evaluation and development tools. How to download the associated API. How to control through the API. The range feature. The ALS feature. Several VL6180X in a design. Figure 1. VL6180X December 2015 DocID Rev 1 1/

2 Contents UM1983 Contents 1 Document references Hardware information Application information Block diagram Schematic Mechanical data Recommended solder pad dimension and reflow profile Evaluation and development tools Application program interface (API) overview API download Quick start guide for API integration Main feature definitions VL6180X range feature Typical ranging output Targets Range output without cover glass Range output with cover glass Convergence time VL6180X Initialization Offset calibration Cross-talk compensation Single range measurement in polling mode Single range measurement in non polling mode Continuous range measurement Early convergence estimate (ECE) Wrap around filter (WAF) Dmax Range status error code information / DocID Rev 1

3 Contents 6 Ambient light sensor mode (ALS) Overview Ambient light sensor settings Analog gain Integration time Cover glass calibration Single ALS measurement in polling mode Interleaved mode Multiple VL6180X application VL6180Xs control management VL6180Xs API management Glossary Revision history DocID Rev 1 3/

4 Document references UM Document references Table 1. Document references Description Datasheet - VL6180X proximity and ambient light sensing (ALS) module Data brief - Proximity, gesture, ambient light sensor expansion board based on VL6180X for STM32F401RE Data brief - Proximity, gesture, ambient light sensor expansion board based on VL6180X for STM32L053R8 Data brief - Proximity and ambient light sensor expansion board based on VL6180X for STM32 Nucleo Data brief - P-NUCLEO-6180X1 and P-NUCLEO-6180X2 packs PC graphical user interface (GUI) Data brief - Proximity, gesture, ambient light sensor software expansion for STM32Cube Data-brief - VL6180X application programing interface (API) Data-brief - VL6180X satellite boards compatible with VL6180X boards DocID DocID DocID DocID DocID DocID DocID DocID DocID / DocID Rev 1

5 Hardware information 2 Hardware information 2.1 Application information Block diagram Figure 2. Block diagram VL6180X module embeds: a VCSEL IR emitter a VL6180X silicon which embeds: a range sensor an ambient light sensor (ALS) a microcontroller and its associated RAM a non volatile memory (NVM) to store sensor default configuration data. DocID Rev 1 5/

6 Hardware information UM Schematic Figure 3. Application schematic Table 2. Pin descriptions Pin number Signal name Description 1 GPIO1 Open drain interrupt output 2 NC No connect 3 NC No connect 4 GPIO0 Chip enable 5 SCL I2C serial clock 6 SDA I2C serial data 7 NC No connect 8 AVDD_VCSEL VCSEL power supply 2.6 to 3.0V 9 AVSS_VCSEL VCSEL ground 10 AVDD Digital/Analog power supply 2.6 to 3.0V 11 NC No connect 12 GND Digital/Analog ground 6/ DocID Rev 1

7 Hardware information Mechanical data Figure 4. Mechanical drawing Recommended solder pad dimension and reflow profile Figure 5. Solder pattern DocID Rev 1 7/

8 Hardware information UM1983 Figure 6. Reflow profile Table 3. Recommended reflow profile Profile Ramp to strike Temperature gradient in preheat (T= C): 0.9 +/- 0.1 C/s Temperature gradient (T= C): C/s Peak temperature in reflow 237 C C Time above 220 C Temperature gradient in cooling Time from 50 to 220 C 50 +/- 10 seconds -1 to -4 C/s (-6 C/s maximum) 160 to 220 seconds Note: As the VL6180X package is not sealed, only a dry re-flow process should be used (such as convection re-flow). Vapor phase re-flow is not suitable for this type of optical component. The VL6180X is an optical component and as such, it should be treated carefully. This would typically include using a no-wash assembly process. 2.2 Evaluation and development tools Several tools can be ordered on in Design Resources page to evaluate and develop applications around the VL6180X (see Figure 7): X-NUCLEO-6180XA1: VL6180X expansion board compatible with the STM32 Nucleo board family and with the Arduino UNO R3 connector layout. P-NUCLEO-6180X1: evaluation pack composed of a X-NUCLEO-6180XA1 expansion board and a powerful STM32F401RE Nucleo board. P-NUCLEO-6180X2: Evaluation pack composed of a X-NUCLEO-6180XA1 expansion board and a ultra low power STM32FLO53R8 Nucleo board. VL6180X-SATEL: Hardware add-on to X-NUCLEO-6180XA1 expansion board to enable multi VL6180X sensor applications 8/ DocID Rev 1

9 Hardware information Figure 7. VL6180X evaluation and development tools Information on the installation of the different softwares allowing the evaluation and the application development around VL6180X are given in the user manual UM1876 Getting started with VL6180X proximity, gesture, ambient light sensor software expansion for STM32Cube. DocID Rev 1 9/

10 Application program interface (API) overview UM Application program interface (API) overview This chapter details the download and the installation of the API. The VL6180X API is a set of C functions controlling the VL6180X (init, ranging, ALS, ) to enable the development of end-user applications. This API is structured in a way it can be compiled on any kind of platform through a well isolated platform layer (mainly for low level I2C access). Several code examples are provided to show how to use the API and perform ranging and ALS measurements. A complete Nucleo F401 + VL6180X expansion board project is also provided (Keil IDE required to compile the project) as well as the pre-compiled binary that can be directly used. 3.1 API download To download the VL6180X API (see:figure 8) on search for VL6180X on next page select: VL6180X On next page select design resources On design resources page select STSW-IMG003 On next page download 10/ DocID Rev 1

11 Application program interface (API) overview Figure 8. API download DocID Rev 1 11/

12 Application program interface (API) overview UM Quick start guide for API integration API documentation is in the docs folder and is available in two formats: API_Documentation_proximity.chm API_Documentation_proximity.html The VL6180X API is integrated in a software project in two steps 1. Developer has to add/link the files listed in Table 4 and in Figure 9 to his source and include code path. Some files may require modification to comply with the final application or the hardware/software capabilities. Table 4. API header files Names Description vl6180x_cfg.h vl6180x_api.c and vl6180x_api.h vl6180x_def.h vl6180x_platform.h vl6180x_types.h Application configuration May require modification All operating functions at high and low level to control the sensor Must not be modified Definition of constants and structures used in the API Must not be modified Target platform specific declarations/prototypes May require modification Basic types definition May require porting Note: 2. To manage the data communication between the VL6180X and the host, the developer has to design a camera control interface (CCI) register communication driver. The API low-level functions rely on the following set of 7 read & write functions which perform CCI register access to the device: VL6180x_WrByte(); VL6180x_WrWord(); VL6180x_WrDWord(); VL6180x_UpdateByte(); VL6180x_RdByte(); VL6180x_RdWord(); VL6180x_RdDWord(). To implement these 7 functions, it is recommended to use vl6180x_i2c.c and vl6180x_i2c.h files in platform/cci_i2c directory (see Figure 9) Detailed information on these functions can be found in section Modules/CCI to RAW I2C translation layer of the API_Documentation_(version)_proximity.chm delivery 12/ DocID Rev 1

13 Application program interface (API) overview Figure 9. Iheader and CCI service files in the API DocID Rev 1 13/

14 Main feature definitions UM Main feature definitions This chapter gives the definition of the main VL6180X features described in this user manual. Ranging Measurement of the distance between VL6180X and the target. Upscale support - Extended range Note: Upscale factor = 1, VL6180X measures distances up to 20cm with a granularity of 1mm. Upscale factor = 2, VL6180X measures distances up to 40cm with a granularity of 2mm. Upscale factor = 3, VL6180X measures distances up to 60cm with a granularity of 3mm. VL6180X ranging performances are specified up to 10 cm. Wrap around filter (WAF) In specific conditions, when targeting a mirror or a very reflective metal, a wrap around effect can occur internally to the VL6180X which results in a wrong distance being returned (under estimated). The goal of the wrap around filter is to detect this wrap around effect and to filter it by returning a non-valid distance. Dmax Estimation of the maximum distance (in mm) up to which the VL6180X will report a valid measurement with a 17% grey target for the current ambient light conditions. Dmax decreases when ambient light increases. Ambient Light Sensor (ALS) Measurement in Lux of the ambient light of the scene. 14/ DocID Rev 1

15 VL6180X range feature 5 VL6180X range feature 5.1 Typical ranging output Targets For the purposes of this document all targets are referred to in terms of their photopic (visible spectrum) reflectance. It should be noted that the photopic reflectance of a target is not necessarily the same as the reflectance at 850nm (the wavelength of the VL6180X emitter). Note: Unless otherwise specified, all targets referenced in VL6180X documentation are Munsell neutral color (gray) charts from X-rite ( filling the entire field of view. The Munsell notation and reflectance is listed here for each target used. N2.00/M 3% Black N2.75/M 5% Black N4.75/M 17% Gray N9.50/M 88% White /M refers to a matt finish on the target Range output without cover glass Figure 10 shows the typical ranging output from VL6180X for different targets at different distances. The test is performed in the dark. Figure 10. Graph of range output vs. target distance without cover glass. DocID Rev 1 15/

16 VL6180X range feature UM1983 The range output of VL6180X with each of the targets should be linear with range. There could however be an offset error. This error can be corrected by performing an offset calibration, see Section 5.4. Note: Note: See also the VL6180X datasheet for the specification on offset error At <10mm the interaction between the target and the VL6180X will prevent the range output from reaching 0mm. This is due to a number of physical effects: Separation between VCSEL and return array Multiple reflections between target surface and the VL6180X VCSEL output penetrating the target surface and scattering off the layers inside the target Range output with cover glass The VL6180X should be used with a cover glass. The cover glass can cause internal reflection and this can be detected by the VL6180X as unwanted signals. This is known as the cross talk. The cross talk can affect the range output, hence we recommend the user perform the cross talk compensation calibration procedure when using the VL6180X with cover glass (see Section 5.5). Figure 11 shows the impact of the cover glass on the range output of the VL6180X. The internal reflection between the glass and the VL6180X causes the ranging output to decrease at longer distances. This error in range is a ratio of the target signal rate and magnitude of the cross talk, hence the range output from a darker target is more susceptible to the effect of cross talk. Figure 12 shows the range output from the VL6180X with the cross talk compensation calibration procedure implemented. The range error caused by the cover glass is corrected. The tests are performed in the dark. Note: The offset might need to be re-calibrated when ranging though cover glass. Offset calibration should always be done before cross talk compensation. The cross talk rate depends on the glass type and its placement relative to the VL6180X. If the glass type or its position changes, then cross talk compensation calibration might need to be re-done. 16/ DocID Rev 1

17 VL6180X range feature Figure 11. Graph of range output vs. target distance with cover glass and without cross talk compensation calibration. Figure 12. Graph of range output vs. target distance with cover glass and cross talk compensation calibration DocID Rev 1 17/

18 VL6180X range feature UM Convergence time Note: Figure 13 shows the typical convergence time output from VL6180X for different targets at different distances. The convergence time can provide useful information on how to optimise VL6180X settings to perform more efficiently and reliably. The test is performed in the dark and with no cover glass. Cover glass can alter the return convergence time characteristics. We therefore recommend the convergence time be re-characterized once the VL6180X has been integrated into the final system before attempting to perform any system optimization. Figure 13. Graph of convergence time vs. target distance 18/ DocID Rev 1

19 VL6180X range feature 5.3 VL6180X Initialization Figure 14 shows the initialization of the VL6180X in the system Figure 14. VL6180X initialization VL6180X set up in the system The user has to set all variables linked to the integration of the VL6180X in its application (e.g.: VL6180X I2C 7 bit default address = 0x29) VL6180x_InitData (One time device initialization) Enables common functions, ie, WAF, ECE, upscaling. Expects device to be fresh out of reset. VL6180x_Prepare (Prepare device for operation) Programs common default settings. Prepares the VL6180X for new ranging or ALS measurement. DocID Rev 1 19/

20 VL6180X range feature UM Offset calibration Place a target with a reflectance of 88% or higher (white target) at 50mm away from VL6180X if Upscale factor is 1 or at 100mm if Upscale factor is 2 or 3. Figure 15. Offset calibration environment Then follow the flow described in Figure / DocID Rev 1

21 VL6180X range feature Figure 16. Offset calibration flow DocID Rev 1 21/

22 VL6180X range feature UM Cross-talk compensation Cross-talk compensation must be run after offset calibration. If the offset is incorrectly calibrated, cross-talk compensation will be inaccurate. Place a target with a low reflectance e.g. 17% reflectance target (gray target) at 100mm away from VL6180X if Upscale factor is 1 or at 400mm if Upscale factor is 2 or 3. Figure 17. Cross-talk compensation environment Then follow the flow described in Figure / DocID Rev 1

23 VL6180X range feature Figure 18. Cross-talk compensation factor setting flow DocID Rev 1 23/

24 VL6180X range feature UM Single range measurement in polling mode Figure 19 shows the flow for a single range measurement in polling mode. Figure 19. Single range measurement flow 24/ DocID Rev 1

25 VL6180X range feature 5.7 Single range measurement in non polling mode This is suitable for applications where host CPU is triggered on an interrupt, not coming from VL6180X, to perform range measurement. Figure 20 shows the flow for a single range measurement in non polling mode. Figure 20. Flow for a single range measurement in non polling mode DocID Rev 1 25/

26 VL6180X range feature UM Continuous range measurement In this mode the host is interrupted by VL6180X. Figure 21 shows the flow for a continuous range measurement. Figure 21. Flow for a continuous range measurement 26/ DocID Rev 1

27 VL6180X range feature 5.9 Early convergence estimate (ECE) Early convergence estimate (ECE) is a programmable feature which is designed to minimize power consumption when there is no target in the field of view (FOV). This feature should only be used when Upscaling is set to 1. The ECE enables the device to decide whether or not there is a target in the FOV and if it should stop the measurement before the default max convergence time is reached to save power. ECE works by calculating the rate of convergence 0.5ms after the measurement has been started. If the return count rate reported by the device is below the set ECE threshold, the measurement is aborted. The ECE feature is enabled through VL6180X_RangeSetEceState function. The ECE return count rate threshold is set through VL6180X_RangeSetEceFactor function. Figure 22 and Figure 23 show examples with a threshold ratio of 0.8 and of 1.1. Figure ECE factor (80%) 80% ECE factor - if the return signal count is above 80% of the ideal convergence rate after 0.5ms of the measurement starting then the system will allow the measurement to continue. DocID Rev 1 27/

28 VL6180X range feature UM1983 Figure ECE factor (110%) 110% ECE factor - if the return signal count is 110% of the ideal convergence rate after 0.5ms of the measurement start, then the system will allow the measurement to continue. This is beneficial if the user wants to have much better power savings as it will only allow a measurement when there is a material or object in front of the sensor. Table 5 gives an example of the current consumption of the VL6180X without and with ECE feature enabled and for a range of inter-measurement periods. In this example, the max convergence time is 50ms. The ECE ratio is set to 95%. Table 5. VL6180X current consumption versus ECE feature and inter-measurement period (in ma) Inter measurement period (ms) ECE = ON ECE = OFF No Target No Target 50mm 100mm Wrap around filter (WAF) Mirrors are high reflective targets and placed at a far distance, more than 60cm, from VL6180X they could still produce enough return signal to declare for VL6180X a valid target resulting in a wrong, under-estimated, returned distance 28/ DocID Rev 1

29 VL6180X range feature WAF function is automatically able to detect such targets and to return the Measured filtered by WAF error 16 (see Table 6). WAF function is enabled through VL6180X_FilterSetState Dmax Dmax feature is enabled through VL6180x_DMaxSetState function. When ambient light level increases, the max detection range (Dmax) decreases, so a target may not be detected by the VL6180X because it is too far for a given ambient light condition. When no target is detected, no valid distance reported, Dmax function is able to define the maximum distance up to which a 17% reflective target is detected with the current ambient light condition Range status error code information Detailed explanation of error code information are given in VL6180X API Integration Guide.pdf on in Design Resources page. Table 6 gives a summary of the meaning of each range status error code. Table 6. Status error code meaning Code Name Comment 0 0b0000 No error Valid distance 1 0b0001 VCSEL_Continuity_Test 2 0b0010 VCSEL_Watchdog_Test 3 0b0011 VCSEL_Watchdog 4 0b0100 PLL1_Lock 5 0b0101 PLL2_Lock 6 0b0110 Early_Convergence_Estimate This error can only happen at the first boot-up. Device needs to be reset to clear the error. If the error persists, then device is defective and must be replaced. If Early Convergence Estimate function (ECE) is enable, no valid target detected after early convergence estimate time. 7 0b0111 Max_Convergence No valid target detected after maximum convergence time. 8 0b1000 No_Target_Ignore Ignore threshold check failed. 9 0b b1010 Not used 11 0b1011 Max_Signal_To_Noise_Ratio Too much ambient light detected 12 0b1100 Raw_Ranging_Algo_Underflow 13 0b1101 Raw_Ranging_Algo_Overflow 14 0b1110 Ranging_Algo_Underflow Could happen If target is between 0 and 10mm and offset is not correctly set. Could happen if the target is detected at a distance higher than 55 cm for upscaling = 3, 20 cm for upscaling = 1. Error is due to internal variables/registers overflow. Could happen If target is between 0 and 10mm and offset is not correctly set. DocID Rev 1 29/

30 VL6180X range feature UM1983 Table 6. Status error code meaning (continued) Code Name Comment 15 0b1111 Ranging_Algo_Overflow 16 0b10000 Filtered by post-processing 18 0b10010 DataNotReady Could happen if the target is detected at a distance higher than 55 cm for upscaling = 3, 20 cm for upscaling = 1. Error is due to internal variables/registers overflow. If Wrap Around Filter is enabled, this error gives the information that a bright target is detected between 60 and 120cm. This error is returned by the VL6180X_RangeGetMeasurementIfReady API function when ranging sample data is not ready. 30/ DocID Rev 1

31 Ambient light sensor mode (ALS) 6 Ambient light sensor mode (ALS) 6.1 Overview The VL6180X can measure the incoming ambient light over a wide dynamic range. The ALS sensor uses a photopic filter in order to approximate the spectral response of the human eye. The raw data output is proportional to the amount of light within the field of view during the integration time. The VL6180X has a typical 42 degree field of view (half angle, 40% of peak) in both X and Y (see Figure 24). Figure 24. ALS angular response The ALS count is converted in lux by the VL6180x_AlsGetLux API function. Lux is the standard unit of light intensity or measurement of the amount of perceived light in an area. Table 7 shows some typical examples of lux values for different conditions. Table 7. Typical lighting conditions Illuminance (lux) Scene description Moonless overcast night Moonless clear night Full moon on clear night 1 Twilight 50 Typical family room lighting 80 Typical office / Hallway lighting 100 Dark overcast day 400 Sunrise or sunset on clear day 1000 Overcast day, typical TV studio lighting DocID Rev 1 31/

32 Ambient light sensor mode (ALS) UM1983 Table 7. Typical lighting conditions Illuminance (lux) Scene description 10,000-25,000 Clear day, indirect sunlight 32, ,000 Direct sunlight 6.2 Ambient light sensor settings Analog gain Analog gain is selected to match the ALS dynamic range to the expected light range of the application and to compensate for the use of cover glass. Analog gain is set through VL6180x_AlsSetAnalogueGain Table 8 gives the dynamic range without and with a 10% transmissive cover glass versus the analog gain values. Table 8. ALS dynamic range (1) Analog gain Dynamic range (No cover glass) Dynamic range (10% transmissive cover glass) Min (Lux) (2) Max (Lux) Min (Lux) Max(Lux) , > 100, , > 100, , > 100, , , , , , , , , , ALS lux resolution 100ms integrated period 2. Minimum ALS count Integration time The ambient light sensor works by counting photons over a fixed time period referred to as the integration time. The resulting output value is proportional to the amount of light sensed or photons received during the integration period. VL6180X is set in the factory to match 0.32 lux per ALS count at an integration time of 100ms. The 100ms integration time is optimal for most applications. It is recommended to adjust the analog gain setting for different light level applications rather than adjusting integration time. When necessary, the integration time can be changed. For example, when the sample rate is required to be faster than the 100ms integration time allowed, decreasing the integration time will allow for faster sampling rates. Lowering the integration time will, however, 32/ DocID Rev 1

33 Ambient light sensor mode (ALS) increase the effect of the light flicker on the result. It is recommended to keep integration time in steps of 50ms to reduce the impact of light flicker. Integration time value is set through VL6180x_AlsSetIntegration Period. 6.3 Cover glass calibration The use of cover glass in an application will block a percentage of light measured at the sensor. This reflected or absorbed light by the glass needs to be accounted for when converting the ALS count to lux. The calibration of the cover glass is only needed when the cover glass is modified. Like ALS lux resolution, the calibration is only used in the conversion from ALS counts to lux and is not written to the VL6180X. To calibrate for cover glass, the device should be placed under a stable light source similar in color temperature and intensity as the application. Multiple ALS measurements are taken both with and without the cover glass. The calibration factor is the ratio of the averaged results: Cover Glass Cal Factor = Avg without glass / Avg with glass 6.4 Single ALS measurement in polling mode Figure 25 shows the flow for a single ALS measurement in polling mode. Figure 25. Single ALS measurement flow DocID Rev 1 33/

34 Interleaved mode UM Interleaved mode Interleaved mode is when a range measurement is immediately followed by an ALS measurement and repeated after an interval specified by the ALS inter-measurement period. Figure 26. Interleaved mode For interleaved mode, ALS feature must be enabled by setting VL6180x_ALS_SUPPORT. Figure 27. Interleaved flow 34/ DocID Rev 1

35 Multiple VL6180X application 8 Multiple VL6180X application This chapter shows how multiple VL6180X devices can be used on a board design while only using a single I2C interface to interact with all the devices. Each VL6180X device has both a reset pin and an interrupt pin, which can be used to enable a multiple device setup. 8.1 VL6180Xs control management Figure 28 is a typical example schematic using a VL6180X device. Since the VL6180X can have the I2C device address changed by doing an I2C write once it is booted, a separate reset pin would be needed to each VL6180X used in a design. Each device is then taken out of reset one at a time, and then the I2C Device Address is changed to a new unique address. This can be done by using multiple GPIO pins from the host on the board. Figure 28. VL6180X typical application Depending of the number of VL6180X used in a design and the number of available GPIO pins from the host, a GPIO expander may be required to manage the reset (GPIO0) and the interrupt (GPIO1) pins of the VL6180Xs. DocID Rev 1 35/

36 Multiple VL6180X application UM VL6180Xs API management See also VL6180X_API_Integration Guide.pdf on in Design Resources page. In vl6180x_platform.h API file Set VL6180x_SINGLE_DEVICE_DRIVER macro to 0 so that API implementation will be automatically adapted to a multi-device context. Define VL6180xDev_t type as a structure pointer holding any data required for multidevice management. A mandatory field is an instance of VL6180xDevData containing ST API private data. Then define, N the number of VL6180X (Struct MyVL6180Dev_t BoardDevs[N] Put all devices under reset One after the other enable VL6180X and set their I2C address through VL6180x_SetI2CAddress (&BoardDevs[i], FinalI2cAddr) 36/ DocID Rev 1

37 Glossary 9 Glossary Table 9. Glossary Term ALS API ECE FOV NVM PCB RAM VCSEL WAF Description Ambient Light Sensor Application Program Interface Early Convergence Estimate Field Of View Non Volatile Memory Printing Circuit Board Random Access Memory Vertical Cavity Surface Emitting Laser Wrap Around Filter DocID Rev 1 37/

38 Revision history UM Revision history Table 10. Document revision history Date Revision Changes 01-Dec Initial release. 38/ DocID Rev 1

39 IMPORTANT NOTICE PLEASE READ CAREFULLY STMicroelectronics NV and its subsidiaries ( ST ) reserve the right to make changes, corrections, enhancements, modifications, and improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on ST products before placing orders. ST products are sold pursuant to ST s terms and conditions of sale in place at the time of order acknowledgement. Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design of Purchasers products. No license, express or implied, to any intellectual property right is granted by ST herein. Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product. ST and the ST logo are trademarks of ST. All other product or service names are the property of their respective owners. Information in this document supersedes and replaces information previously supplied in any prior versions of this document STMicroelectronics All rights reserved DocID Rev 1 /